Metal composition



Patented May 16, 1939 PATENT OFFICE METAL COMPOSITION Samuel Ruben, New Rochelle, N. Y.

No Drawing. Application November 12, 1935, Serial No. 19,351

'5 Claims. (cl. 75-170) This invention relates to a metal composition.

An object of the invention is the provision of a metal composition suitable ior use as a cathode member.

Another object is the provision of an electrode material having incorporated thereina stable low work function compound which is electrically conductive at room temperature.

a further object is the provision of an alloy composed of a base material such as nickel or nickel and chromium with which has been incorporated a very small amount of a silicide oi one or more of the allraline earth metals strontium, barium or calci..

in the prior art there are metal compositions oi niclrel and barl, ior instance, in the patent to having, 11,636,763, there is disclosed a material' iormed irom adding barium to nichel in powdered form, the ,mass being sintered and molded into the desired shape. However, the use of barium lnthe metallic state is undesirable in a great many instances, because of the invariable tendency oi the metal to form its aside. it is well known that barium, when erposed to the atmosphere, will not remain as harium but will form harium oxide, which. is an insulator at ordinary temperatures and which requires heating to render it electrically conductive. The use oi one or more oi the alkaline earth silicldes, which require no heating to hecome conductive and which are remarkably stable, callers important advantages and improvements over the use of the allraline metals or their asides. l have found that a composition composed o nickel and l% or less of a silicide of barium, strontium or calcium is especially adapted ior use in the fabrication oi cathodes. it. specific use tor the material is its iahrication into spar-l; plug electrodes.

Generally, the composition may be said to be formed from 01.5% to asses, niclrel or niclrel chromium and 0.105% to 2.5% alltaline earth silicide. l preier to use the materials in the lollowing ranc'es:

- Alkaline earth silt N ickel Gide Percent 0.05 to 2.5

Percent 97. 5 to 99.95 Y

Chromium Alkaline earth sili- Nickel cida Percent 0.05 to 2.5

Percent l to 6 Percent 91.5 to 98.95

With either of the two above compositions, it

may be of advantage to employ a fractional per cent of a scavenger material. A suitable com pound for this purpose is magnesium silicide, which may be added up to 0.5%.

In the preparation of a typical composition, I use 99% nickel and 1% of an equimolar mixture of strontium and barium silicides, the materials being in finely divided form, and to these I add 0.5% magnesium silicide as a'scavenger. The various constituents are pressed into a high density rod which is sintered or welded by discharging a high current density therethrough. The current and temperature required will depend upon the particular proportions used and the pressure of the surrounding atmosphere. in most cases, a temperature of about 1500 C. will sufhce.

The sintering and welding of the finely divided materials into a homogeneous mass is preferably accomplished in an inert atmosphere of helium or ii the temperature is controlled, hydrogen can he used. 0

its stated above, the magnesium silicide may be omitted, ii desired, as it is used chiefly as a scavenger and to produce a rod at higher density. The latter erect is prchahly due to partial dissociation oi the magnesium silicide and the I production oi some free magnesium.

The mixture oi? barium and strontiumsilicide has been found to be somewhat better than either one alone although for practical purposes the sillcide of barium, strontium or calcium may be employed.

The addition oi chromium limits oxidation and corrosion and it may be added either in elemental term or as an alloy oi niclrel. l have described a method of preparing the composition by mixing the ingredients in finely divided form, pressing and sintering at a high temperature but if desired the nickelor nickel chromium may be heated and the silicide added at the melting point.

Where the composition is drawn to wire form and wed in the fabrication of spark plug electrodes, the silicide content is preferably kept below 1% and it has been found that 0.2% is quite ample to secure the desired characteristics. The maximum percentage of alkaline earth silicide combined with the nickel or nickel chromium base is dependent upon the degree of malleability desired in the finished product. The useful range of silicide appears to be from 0.05% to 2.5%.

Cobalt may be used as a substitute in whole or in part for the nickel but because of the wide difference in cost, nickel is preferred.

This invention does not exclude the addition to the composition of other elements which have the effect chiefly of diluting the nickel and the presence of which does not seriously impair the benefits and advantages derived from the use oi.

the alkaline earth silicide. Obvious variations in the composition and the use of equivalents which do not substantially alter the advantages obtained by the present invention are considered to be within the scope of the present application.

Having described by invention, what I claim 1. A metal composition composed of nickel,

l5 cide, about 0.05% to 2.5%.

4. A metal composition composed oi! 0.05% to 2.5% of an alkaline earth silicide and the remainder substantially all nickel characterized by a low work function and by greater constancy of electrical conductivity with variations in tem perature than a similar composition containing alkaline earth oxides in place of said alkaline earth slllcides. 4

5. A spark plug electrode composed of 0.05% to 2.5% of an alkaline earth silicide and the remainder substantially all nickel characterized by a low work function and by greater constancy of electrical conductivity with variations in temperature than a similar composition containing alkaline earth oxides in place of said alkaline earth silicides.

SAMUEL RUBEN. 

